CA2027655C - Lightning protection apparatus for rf equipment and the like - Google Patents
Lightning protection apparatus for rf equipment and the likeInfo
- Publication number
- CA2027655C CA2027655C CA002027655A CA2027655A CA2027655C CA 2027655 C CA2027655 C CA 2027655C CA 002027655 A CA002027655 A CA 002027655A CA 2027655 A CA2027655 A CA 2027655A CA 2027655 C CA2027655 C CA 2027655C
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- Prior art keywords
- equipment
- antenna
- lightning
- coupled
- capacitor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/50—Structural association of antennas with earthing switches, lead-in devices or lightning protectors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/201—Filters for transverse electromagnetic waves
- H01P1/202—Coaxial filters
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Emergency Protection Circuit Devices (AREA)
- Details Of Aerials (AREA)
Abstract
Lightning protection apparatus for antenna-coupled RF
equipment is provided. A one quarter wavelength shorting stub bandpass filter shunts the RF equipment and a distributed capacitance, high voltage coaxial capacitor is serially coupled between the equipment and antenna. The shorting stub is tuned to one quarter wavelength of the RF equipment operating frequency.
The series capacitor passes frequencies at or above the operating frequency of the RF equipment.
equipment is provided. A one quarter wavelength shorting stub bandpass filter shunts the RF equipment and a distributed capacitance, high voltage coaxial capacitor is serially coupled between the equipment and antenna. The shorting stub is tuned to one quarter wavelength of the RF equipment operating frequency.
The series capacitor passes frequencies at or above the operating frequency of the RF equipment.
Description
~,~,i.7~
This invention relates to communications and other eiectronics systems which utilize antennas which are exposed to lightning and similar environmental disturbances and more particularly to lightning protection apparatus for such systems.
Receiving and transmitting antennas for radio and other RF equipment are often positioned as high as possible above the ground and are usually arranged to be above trees and other structures. Accordingly, they are very likely to attract lightning strokes or to be affected by near misses. When the antenna is struck by lightning or is even subject to a near miss, a surge o~
current of a very high order of magnitude is induced in the antenna and transmitted to the RF equipment to which the antenna is coupled. Needless to say, it is necessary to protect RF equipment from the high current and voltages to which they may be subjected by such atmospheric events.
Lightning usually consists of one or more pulses having a short rise time and a long decay time. The currents induced by lightning could range into the thousands of ampers. One known method of protecting against current and voltage surges is a series 2Q circuit breaker. This may take several forms, such as a fuse, an electromechanical circuit breaker or a self-triggering solid state circuit breaker, for example. Unfortunately, each of these devices has a relatively long operating time delay which may permit the equipment bein~ protected to be damaged. Additionally, these devices disturb the operation of the equipment being protected by preventing operation of the equipment until the device is repaired or reset. Another method of protecting antenna coupled RF
e~uipment is to employ a shunt or bypass device that would either dissipate the energy of the lightning stroke or bypass it to ground. Many of these devices are also subject to the operating time delay and need to repair/reset ills to which the series circuit breaker devices are subject. A third method of protection is the tuned or selective type of protection system which will allow only the desired RF signals or "traffic" to flow to/from the antenna but will divert or bypass the harmful energy of the lightning occurrence. It is this method with which the p;resent invention is concerned.
It is an object of this invention to provide lightning protection apparatus for RF equipment coupled to an antenna which comprises a passive electrical system which will cause little, iE
any, interference with the operation of the RF equipment. The lightning protection apparatus also mechanically rugged in construction, is relatively easy to fabricate and install, contains no moving parts and need not be reset or repaired after operation.
Briefly, the ~ightning protection apparatus for RF
equipment coupled to an antenna comprises a high pass filter serially coupled between the antenna and the RF equipment and a bandpass filter shunted across the RF equipment. The high pass filter is operative to pass frequencies which are approximately at and above the operating frequency of the RF equipment. The bandpass filter is operative to prevent frequencies which are below the operating frequency of the RF equipment from reaching the RF
equipment. As will be explained hereinafter, most of the high energy frequencies which are induced in the antenna by lightning are usually below the operating frequency of the RF equipment and are therefore prevented from reaching the RF equipment. The rJ U v' ~
invention provides that the bandpass ~ilter may comprise a shorting stub having a length equal to one quarter of a wavelength of the operating frequency of the RF equipment. The high pass filter may be a capacitive reactance impedance which is formed by a cylindrical capacitor having a capacitance distributed along the length of the capacitor. If desired, lightning arrestors for personnel protection may be located at strategic points.
The nature of the invention and other objects and additional advantages thereof will be more readily understood by those skilled in the art after consideration of the following detailed description taken in conjunction with the accompanying drawings.
In the drawings:
Figure 1 is a graphical representation showing current as a function of time for both hot and cold types of lightning surges;
Figure 2 is a schematic diagram of the lightning protection apparatus of the invention coupled between an antenna and an item of RF equipment;
Figure 3 is a schematic diagram of a high voltage coaxial capacitor which is suitab'e for use as the series high pass filter of the apparatus of the invention; and Figure 4 is a schematic diagram of another type of high voltage coaxial capacitor which is suitable for use as the series high pass filter of the apparatus of the invention.
Referring to the drawings, the graphical representation of Figure 1 shows the current flowing in the temporarily conductive air path of a typical lightning stroke to ground. The ordinates of this representation are in thousands of amperes. If the lightning ~7i~ ~ 7 stroke itself is considered to be a half-turn primary winding of a transformer and the antenna system the half-turn secondary winding of a loose-coupled transformer, it is easily seen how a voltage may be generated in the antenna system by the lightning stroke. The induced voltage would be a function of many factors, such as the equivalent impedance between the two ends of the transformer secondary, the degree of coupling, etc. and could easily exceed thousands of volts.
It can be shown that the energy of a lightning stroke, as a function of frequency, is given by the following equation:
G(f) = Aetp (1 ~ j2~tp where, A = peak value of current e = 2.71828 tp = 5 x 10-6 seconds f = frequency of interest in hertz.
From the foregoing equation it is evident that the energy content is maximum at dc and rapidly falls as the frequency rises. The following Table 1 computes the energy at various discrete frequency bands normalized to that at dc.
At Frequencies above f Calculated Attn. Per Ref/C
f j2~tpf Fraction Percent dB MV/m Ref to * Approx dB
DC 0 1~0 100 0 1 KHZ O 1 . O 100 0 10 KHz* O.3 0.6 60 22 x 104 1 0 10100 XHz 3.1 lO-l 10 lO2 x 103 lO-l 20 1 MHz 31.4 10-3 0-1 302 x 1021o 2 40 10 MHz 314 10-5 0.001 50 10 5 x 10 3 66 100 MHz 3.140 ~070.00001 70 2 10 4 80 GHz 31.400 1090.0000001 903 x 10115 x 10' 96 The foregoing table shows that for frequencies of interest in the microwave range, eliminating the energy below the frequency of interest will divert a major portion of the lightning surge energy away from the RF equipment to be protected.
Referring now to Figure 2 of the drawings, there is shown 20 lightning protection apparatus for RF equipment coupled to an antenna constructed in accordance with the teachings of the present invention. As seen therein, an antenna 10 which may be a receiving or transmitting antenna is coupled by means o~ a coaxial cable, indicated generally as ll, to an item of RF equipment 1 2 which may either provide signals to the antenna 10 for transmission or receive signals which are received by the antenna 10. Although the term "RF equipmentl' is used hereinl it will be understood that the electronic eguip~ent to be protected by the present invention could be any one of a number of differ2nt types of electronic equipment ~ 3~)~
which operate in those regions of the frequency spectrum which utilize antennas for transmission and reception.
In accordance with the invention, a high pass filter, indicated generally as 13, is serially coupled between the antenna 10 and the RF equipment 12. This filter is operative to pass frequencies which are approximately at and above the operating frequency of the RF equipment 12 so that it will not interfere with the reception or transmission of the traffic from/to the antenna.
A bandpass filter, indicated generally as 14, is shunted across the RF equipment 12. The bandpass filter 14 is operative to prevent Erequencies which are received from the antenna 10 which are below the operating frequency of the RF equipment from reaching the RF
equipment. Since the high pass filter 13 is serially coupled between the antenna 10 and the RF equipment 12 and the bandpass filter 14 is arranged to shunt or be in parallel with the RF
equipment 12, the series filter 13 and the shunt filter 14 in effect form a frequency responsive voltage divider with respect to signals received from the antenna and transmitted to the RF
equipment. By virtue of this arrangement, the shunt bandpass filter w~ll prevent those frequencies of the lightning surge received from the antenna 10 which are below the operating frequency of the RF equipment 10 from ever reaching that equipment.
Since, as explained previously, it is this very low range of frequencies which contain the most energy which is harmful to -the equipment being protected, the bandpass filter will provide good, continuous protection for the equipment.
In practice, since the antenna 10 is usually coupled to the RF equipment 12 by means of the coaxial cable 11 illustrated, '~t,~-'J ~
the bandpass filter may conveniently comprise a shorting stub 15 which is connected to the center conductor 16 of the coaxial cable and which has an electrical length equal to one quarter of a wavelength of the operating frequency at which the RF equipment 12 operates. The bandpass filter 14 may, as illustrated, conveniently form part of a T connector having a metallic body 17 which is connected directly to earth ground 18 by means of a suitably strong ground lead 19. The ground lead should preferably be of AWG No. 6 copper braided construction. The equivalent resistance of the shorting stub wo~lcl probably be on the order of 0.01 ohms. If it is assumed that the impedance of the system feeding the component is at least 50 ohms, then the Q of the shorting stub could be around 200. This will define the passband to be approximately f/200 and the rejection loss at 20 log 200, or about 46dB.
The series high pass filter portion 13 of the invention presents a problem because the greater the value of the impedance of this element, the greater is the effectiveness of the protection, however, the greater will be the loss of desirable signal to the RF equipment 12. The series element 13 is intended to enhance the performance of the protection system. It does this by increasing the ratio of the voltage divider formed by the components of the system in the frequency range that is least wanted and contains the most unwanted energy. The use of a capacitive reactance component would perform the foregoing function well because its impedance value would increase with a decrease in frequency which would greatly enhance the separation of the extraneous undesirable lightning energy from the desired signal energy from the antenna. Its value should be such that, at the r~7 ~ r desired frequency, its impedance would be of ~he order of 1 or 2 ohms. Thus, 1 ohm at 1 GHz would be 1,000 ohms at a MHz, 1,000,000 ohms at 1 kH~, etc. A capacitor of 200 microfarads would approximate this performance for the 1 MHz passband.
Figure 3 of the drawings shows a high voltage coaxial capacitor which may be used for the series filter element 13 of the system of the invention. As seen therein, the capacitor comprises a cylindrical fiberglass core 20 around which is concentrically disposed a cylindrical inner conductor 21 of copper foil or other suitable conductive material. The inner conductor ~1 has end 22 thereof electrically connected by means such as soldering, for example, to the metal ferrule 23 of an antenna. The end 24 of thP
antenna 23 is embedded in the fiberglass core 20 of the capacitor.
Shrink tubing 25 is concentrically disposed about the inner conductor 21 and functions as the dielectric of the capacitor.
Shrink tubing may comprise Teflon* or other suitable materials which are insulators with respect to high voltage and which have a suitably high dielectric constant. A cylindrical outer conductor 26 which may also be fabricated of copper foil is cancentrically disposed around the shrink tubing 25. The end 27 of the outer conductor 26 is electrically connected by means such as soldering, for example, to the braid or outer conductor of a coaxial cable or the like which is disposed in a fiberglass envelope 28.
The capacitance of this capacitor will be distributed along the length of the capacitor and will be a function of the amount by which the inner and outer conductors telescope or overlap, the thickness of the shrink tubing and the dielectric constant of the shrink tubing material. This capacitor will not * Trade Mark r~ v 1~ 7 ~ ~ ~
only provide adequate capacitive reactance for the microwave energy being handled but will exhibit a suitably small inductive reactance so that the microwave or other signal being process is not blocked or distorted which might be the case with conventional glass high voltage capacitors. Although antenna ferrules and ~he like and coaxial braid conductors have been shown as the lead elements for this capacitor it is obvious that other connectors could be utilized.
The capacitor shown in Figure 4 of the drawings is an improved version of the capacitor shown in Figure 3. In this arrangement, the two leads or connections to the capacitor are the ferrules 29 and 30 which are the same. Additionally, two capacitances are provided in series. As seen in Figure 4, two axially-separated, cylindrical inner conductors 31 and 32 have a portion of their lengths concentrically disposed within a single, cylindrical outer conductor 33. Again, shrink tubing 34 separates the inner and outer conductors and the interior of the capacitor is the fiberglass core 35. One end 36 of each of the inner conductors 31 and 32 is electrically connected to the metal ferrule ~9 or 30 with which that inner conductor is associatedO In this series capacitance arrangement of the capacitor, the net capacitance with all other dimensions unaltered would be approximately one guarter or the capacitance for the capacitor shown in Figure 3. It may be noted that a fine, close-weave braid may be employed for -the copper foil inner and outer conductors if desired.
In order to reduce the strain on the insulation in the lightning protection apparatus of the invention r it would be advisable to limit the m~;rll~ high voltage encountered at the ~s~7~ ~
antenna itself during a lightning stroke or surge. This may be accomplished by connecting a lightning arrestor 37 between the output of the antenna 10 and earth ground 18 by means of a lead 38.
The ~iring time of the lightning arrestor 37 must be short.
Accordingly, a gas-type, preionized discharge arrestor could be utilized. Additionally, the capacitance between the discharge points of the lightning arrestor should be low enough not to shunt any significant amount o~ the traffic signal energy from the antenna 10. If desired, a similar lightning arrestor 39 and a lead 40 could serve to protect the site of the series high pass filter 13 as illustrated. Finally, for personnel protection the RF
equipment 12 itself should be connected to earth ground by a lead 41.
Using the data developed in Table 1 herein, the following Table 2 was developed for the apparatus of the inventionQ
Table 2 Surqe Enerqy in 1 GHZ System Attenuations Surge Energy dB/s dB/Sh dB/Tot dBR In dBR Out (1) (2) 13) (4) (5) (6) DC
1 KHz gO 40 130 0 - 130 10 KHZ 70 40 110 - O.1 - 110.1 100 KHz 50 40 90 - 10 - 100.
1 MHz 30 40 70 - 30 - 100 10 MHz 9.6 40 40.9 - 50 - 100 100 MHz Q.4 20 20.4 - 70 - 90.4 1 GHz o.o o.g - o~g _ 9O _ 9O 9 10 GHz 0.0 20 20 -110. - 130 Notes: (2) dB~s = Attenuation due to Zs (3) dB/Sh = Attenuation due to Shorting Stu~
(4) dB/Tot = Sum of (2) and (3) (5) dBr In = Incoming surge energy relative to peak (6) dBr Out = Equipment surge energy relative to incomin~ peak The attsnuation figures given in column 2 of this Table are optimistic because they assume that the capacitor will not experience any leakage throughout its life and will maintain a leakage resistance in excess of 16,000 ohms. Failure to do so however may drop the maximum attention to 50 dB. For a 10 MHz system, the s-troke energy would be reduced approximately 50 dB
which is a voltage reduction of about 300:1. For the 100 MHz and 1 GHz points the corresponding voltage reductions would be about 3,000:1 and 30,000:1, respectively.
It is believed apparent that many changes could be made in the construction and described uses of the foregoing lightning protection apparatus and many seemingly different embodiments of the invention could be constructed without departing from the scope thereof. Accordingly, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
This invention relates to communications and other eiectronics systems which utilize antennas which are exposed to lightning and similar environmental disturbances and more particularly to lightning protection apparatus for such systems.
Receiving and transmitting antennas for radio and other RF equipment are often positioned as high as possible above the ground and are usually arranged to be above trees and other structures. Accordingly, they are very likely to attract lightning strokes or to be affected by near misses. When the antenna is struck by lightning or is even subject to a near miss, a surge o~
current of a very high order of magnitude is induced in the antenna and transmitted to the RF equipment to which the antenna is coupled. Needless to say, it is necessary to protect RF equipment from the high current and voltages to which they may be subjected by such atmospheric events.
Lightning usually consists of one or more pulses having a short rise time and a long decay time. The currents induced by lightning could range into the thousands of ampers. One known method of protecting against current and voltage surges is a series 2Q circuit breaker. This may take several forms, such as a fuse, an electromechanical circuit breaker or a self-triggering solid state circuit breaker, for example. Unfortunately, each of these devices has a relatively long operating time delay which may permit the equipment bein~ protected to be damaged. Additionally, these devices disturb the operation of the equipment being protected by preventing operation of the equipment until the device is repaired or reset. Another method of protecting antenna coupled RF
e~uipment is to employ a shunt or bypass device that would either dissipate the energy of the lightning stroke or bypass it to ground. Many of these devices are also subject to the operating time delay and need to repair/reset ills to which the series circuit breaker devices are subject. A third method of protection is the tuned or selective type of protection system which will allow only the desired RF signals or "traffic" to flow to/from the antenna but will divert or bypass the harmful energy of the lightning occurrence. It is this method with which the p;resent invention is concerned.
It is an object of this invention to provide lightning protection apparatus for RF equipment coupled to an antenna which comprises a passive electrical system which will cause little, iE
any, interference with the operation of the RF equipment. The lightning protection apparatus also mechanically rugged in construction, is relatively easy to fabricate and install, contains no moving parts and need not be reset or repaired after operation.
Briefly, the ~ightning protection apparatus for RF
equipment coupled to an antenna comprises a high pass filter serially coupled between the antenna and the RF equipment and a bandpass filter shunted across the RF equipment. The high pass filter is operative to pass frequencies which are approximately at and above the operating frequency of the RF equipment. The bandpass filter is operative to prevent frequencies which are below the operating frequency of the RF equipment from reaching the RF
equipment. As will be explained hereinafter, most of the high energy frequencies which are induced in the antenna by lightning are usually below the operating frequency of the RF equipment and are therefore prevented from reaching the RF equipment. The rJ U v' ~
invention provides that the bandpass ~ilter may comprise a shorting stub having a length equal to one quarter of a wavelength of the operating frequency of the RF equipment. The high pass filter may be a capacitive reactance impedance which is formed by a cylindrical capacitor having a capacitance distributed along the length of the capacitor. If desired, lightning arrestors for personnel protection may be located at strategic points.
The nature of the invention and other objects and additional advantages thereof will be more readily understood by those skilled in the art after consideration of the following detailed description taken in conjunction with the accompanying drawings.
In the drawings:
Figure 1 is a graphical representation showing current as a function of time for both hot and cold types of lightning surges;
Figure 2 is a schematic diagram of the lightning protection apparatus of the invention coupled between an antenna and an item of RF equipment;
Figure 3 is a schematic diagram of a high voltage coaxial capacitor which is suitab'e for use as the series high pass filter of the apparatus of the invention; and Figure 4 is a schematic diagram of another type of high voltage coaxial capacitor which is suitable for use as the series high pass filter of the apparatus of the invention.
Referring to the drawings, the graphical representation of Figure 1 shows the current flowing in the temporarily conductive air path of a typical lightning stroke to ground. The ordinates of this representation are in thousands of amperes. If the lightning ~7i~ ~ 7 stroke itself is considered to be a half-turn primary winding of a transformer and the antenna system the half-turn secondary winding of a loose-coupled transformer, it is easily seen how a voltage may be generated in the antenna system by the lightning stroke. The induced voltage would be a function of many factors, such as the equivalent impedance between the two ends of the transformer secondary, the degree of coupling, etc. and could easily exceed thousands of volts.
It can be shown that the energy of a lightning stroke, as a function of frequency, is given by the following equation:
G(f) = Aetp (1 ~ j2~tp where, A = peak value of current e = 2.71828 tp = 5 x 10-6 seconds f = frequency of interest in hertz.
From the foregoing equation it is evident that the energy content is maximum at dc and rapidly falls as the frequency rises. The following Table 1 computes the energy at various discrete frequency bands normalized to that at dc.
At Frequencies above f Calculated Attn. Per Ref/C
f j2~tpf Fraction Percent dB MV/m Ref to * Approx dB
DC 0 1~0 100 0 1 KHZ O 1 . O 100 0 10 KHz* O.3 0.6 60 22 x 104 1 0 10100 XHz 3.1 lO-l 10 lO2 x 103 lO-l 20 1 MHz 31.4 10-3 0-1 302 x 1021o 2 40 10 MHz 314 10-5 0.001 50 10 5 x 10 3 66 100 MHz 3.140 ~070.00001 70 2 10 4 80 GHz 31.400 1090.0000001 903 x 10115 x 10' 96 The foregoing table shows that for frequencies of interest in the microwave range, eliminating the energy below the frequency of interest will divert a major portion of the lightning surge energy away from the RF equipment to be protected.
Referring now to Figure 2 of the drawings, there is shown 20 lightning protection apparatus for RF equipment coupled to an antenna constructed in accordance with the teachings of the present invention. As seen therein, an antenna 10 which may be a receiving or transmitting antenna is coupled by means o~ a coaxial cable, indicated generally as ll, to an item of RF equipment 1 2 which may either provide signals to the antenna 10 for transmission or receive signals which are received by the antenna 10. Although the term "RF equipmentl' is used hereinl it will be understood that the electronic eguip~ent to be protected by the present invention could be any one of a number of differ2nt types of electronic equipment ~ 3~)~
which operate in those regions of the frequency spectrum which utilize antennas for transmission and reception.
In accordance with the invention, a high pass filter, indicated generally as 13, is serially coupled between the antenna 10 and the RF equipment 12. This filter is operative to pass frequencies which are approximately at and above the operating frequency of the RF equipment 12 so that it will not interfere with the reception or transmission of the traffic from/to the antenna.
A bandpass filter, indicated generally as 14, is shunted across the RF equipment 12. The bandpass filter 14 is operative to prevent Erequencies which are received from the antenna 10 which are below the operating frequency of the RF equipment from reaching the RF
equipment. Since the high pass filter 13 is serially coupled between the antenna 10 and the RF equipment 12 and the bandpass filter 14 is arranged to shunt or be in parallel with the RF
equipment 12, the series filter 13 and the shunt filter 14 in effect form a frequency responsive voltage divider with respect to signals received from the antenna and transmitted to the RF
equipment. By virtue of this arrangement, the shunt bandpass filter w~ll prevent those frequencies of the lightning surge received from the antenna 10 which are below the operating frequency of the RF equipment 10 from ever reaching that equipment.
Since, as explained previously, it is this very low range of frequencies which contain the most energy which is harmful to -the equipment being protected, the bandpass filter will provide good, continuous protection for the equipment.
In practice, since the antenna 10 is usually coupled to the RF equipment 12 by means of the coaxial cable 11 illustrated, '~t,~-'J ~
the bandpass filter may conveniently comprise a shorting stub 15 which is connected to the center conductor 16 of the coaxial cable and which has an electrical length equal to one quarter of a wavelength of the operating frequency at which the RF equipment 12 operates. The bandpass filter 14 may, as illustrated, conveniently form part of a T connector having a metallic body 17 which is connected directly to earth ground 18 by means of a suitably strong ground lead 19. The ground lead should preferably be of AWG No. 6 copper braided construction. The equivalent resistance of the shorting stub wo~lcl probably be on the order of 0.01 ohms. If it is assumed that the impedance of the system feeding the component is at least 50 ohms, then the Q of the shorting stub could be around 200. This will define the passband to be approximately f/200 and the rejection loss at 20 log 200, or about 46dB.
The series high pass filter portion 13 of the invention presents a problem because the greater the value of the impedance of this element, the greater is the effectiveness of the protection, however, the greater will be the loss of desirable signal to the RF equipment 12. The series element 13 is intended to enhance the performance of the protection system. It does this by increasing the ratio of the voltage divider formed by the components of the system in the frequency range that is least wanted and contains the most unwanted energy. The use of a capacitive reactance component would perform the foregoing function well because its impedance value would increase with a decrease in frequency which would greatly enhance the separation of the extraneous undesirable lightning energy from the desired signal energy from the antenna. Its value should be such that, at the r~7 ~ r desired frequency, its impedance would be of ~he order of 1 or 2 ohms. Thus, 1 ohm at 1 GHz would be 1,000 ohms at a MHz, 1,000,000 ohms at 1 kH~, etc. A capacitor of 200 microfarads would approximate this performance for the 1 MHz passband.
Figure 3 of the drawings shows a high voltage coaxial capacitor which may be used for the series filter element 13 of the system of the invention. As seen therein, the capacitor comprises a cylindrical fiberglass core 20 around which is concentrically disposed a cylindrical inner conductor 21 of copper foil or other suitable conductive material. The inner conductor ~1 has end 22 thereof electrically connected by means such as soldering, for example, to the metal ferrule 23 of an antenna. The end 24 of thP
antenna 23 is embedded in the fiberglass core 20 of the capacitor.
Shrink tubing 25 is concentrically disposed about the inner conductor 21 and functions as the dielectric of the capacitor.
Shrink tubing may comprise Teflon* or other suitable materials which are insulators with respect to high voltage and which have a suitably high dielectric constant. A cylindrical outer conductor 26 which may also be fabricated of copper foil is cancentrically disposed around the shrink tubing 25. The end 27 of the outer conductor 26 is electrically connected by means such as soldering, for example, to the braid or outer conductor of a coaxial cable or the like which is disposed in a fiberglass envelope 28.
The capacitance of this capacitor will be distributed along the length of the capacitor and will be a function of the amount by which the inner and outer conductors telescope or overlap, the thickness of the shrink tubing and the dielectric constant of the shrink tubing material. This capacitor will not * Trade Mark r~ v 1~ 7 ~ ~ ~
only provide adequate capacitive reactance for the microwave energy being handled but will exhibit a suitably small inductive reactance so that the microwave or other signal being process is not blocked or distorted which might be the case with conventional glass high voltage capacitors. Although antenna ferrules and ~he like and coaxial braid conductors have been shown as the lead elements for this capacitor it is obvious that other connectors could be utilized.
The capacitor shown in Figure 4 of the drawings is an improved version of the capacitor shown in Figure 3. In this arrangement, the two leads or connections to the capacitor are the ferrules 29 and 30 which are the same. Additionally, two capacitances are provided in series. As seen in Figure 4, two axially-separated, cylindrical inner conductors 31 and 32 have a portion of their lengths concentrically disposed within a single, cylindrical outer conductor 33. Again, shrink tubing 34 separates the inner and outer conductors and the interior of the capacitor is the fiberglass core 35. One end 36 of each of the inner conductors 31 and 32 is electrically connected to the metal ferrule ~9 or 30 with which that inner conductor is associatedO In this series capacitance arrangement of the capacitor, the net capacitance with all other dimensions unaltered would be approximately one guarter or the capacitance for the capacitor shown in Figure 3. It may be noted that a fine, close-weave braid may be employed for -the copper foil inner and outer conductors if desired.
In order to reduce the strain on the insulation in the lightning protection apparatus of the invention r it would be advisable to limit the m~;rll~ high voltage encountered at the ~s~7~ ~
antenna itself during a lightning stroke or surge. This may be accomplished by connecting a lightning arrestor 37 between the output of the antenna 10 and earth ground 18 by means of a lead 38.
The ~iring time of the lightning arrestor 37 must be short.
Accordingly, a gas-type, preionized discharge arrestor could be utilized. Additionally, the capacitance between the discharge points of the lightning arrestor should be low enough not to shunt any significant amount o~ the traffic signal energy from the antenna 10. If desired, a similar lightning arrestor 39 and a lead 40 could serve to protect the site of the series high pass filter 13 as illustrated. Finally, for personnel protection the RF
equipment 12 itself should be connected to earth ground by a lead 41.
Using the data developed in Table 1 herein, the following Table 2 was developed for the apparatus of the inventionQ
Table 2 Surqe Enerqy in 1 GHZ System Attenuations Surge Energy dB/s dB/Sh dB/Tot dBR In dBR Out (1) (2) 13) (4) (5) (6) DC
1 KHz gO 40 130 0 - 130 10 KHZ 70 40 110 - O.1 - 110.1 100 KHz 50 40 90 - 10 - 100.
1 MHz 30 40 70 - 30 - 100 10 MHz 9.6 40 40.9 - 50 - 100 100 MHz Q.4 20 20.4 - 70 - 90.4 1 GHz o.o o.g - o~g _ 9O _ 9O 9 10 GHz 0.0 20 20 -110. - 130 Notes: (2) dB~s = Attenuation due to Zs (3) dB/Sh = Attenuation due to Shorting Stu~
(4) dB/Tot = Sum of (2) and (3) (5) dBr In = Incoming surge energy relative to peak (6) dBr Out = Equipment surge energy relative to incomin~ peak The attsnuation figures given in column 2 of this Table are optimistic because they assume that the capacitor will not experience any leakage throughout its life and will maintain a leakage resistance in excess of 16,000 ohms. Failure to do so however may drop the maximum attention to 50 dB. For a 10 MHz system, the s-troke energy would be reduced approximately 50 dB
which is a voltage reduction of about 300:1. For the 100 MHz and 1 GHz points the corresponding voltage reductions would be about 3,000:1 and 30,000:1, respectively.
It is believed apparent that many changes could be made in the construction and described uses of the foregoing lightning protection apparatus and many seemingly different embodiments of the invention could be constructed without departing from the scope thereof. Accordingly, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
Claims (3)
1. Lightning protection apparatus comprising an antenna;
RF equipment coupled to said antenna; a high pass filter serially coupled between said antenna and said RF equipment, said filter being operative to pass frequencies which are approximately at and above the operating frequency of said RF
equipment and being a coaxial cylindrical capacitor having a capacitance distributed along the length thereof; and a bandpass filter shunted across said RF equipment, said bandpass filter being operative to prevent frequencies which are below the operating frequency of said RF equipment from reaching said RF equipment and comprising a shorting stub having a length equal to one quarter of a wavelength of the operating frequency of said RF equipment.
RF equipment coupled to said antenna; a high pass filter serially coupled between said antenna and said RF equipment, said filter being operative to pass frequencies which are approximately at and above the operating frequency of said RF
equipment and being a coaxial cylindrical capacitor having a capacitance distributed along the length thereof; and a bandpass filter shunted across said RF equipment, said bandpass filter being operative to prevent frequencies which are below the operating frequency of said RF equipment from reaching said RF equipment and comprising a shorting stub having a length equal to one quarter of a wavelength of the operating frequency of said RF equipment.
2. Lightning protection apparatus as claimed in claim 1 wherein a first lightning arrestor is coupled between said antenna and earth ground, and a second lightning arrestor is coupled between said capacitor and earth ground.
3. Lightning protection apparatus as claimed in claim 2 wherein each of said lightning arrestors is a gas-type preionized discharge arrestor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/428,792 | 1989-10-30 | ||
| US07/428,792 US4985800A (en) | 1989-10-30 | 1989-10-30 | Lighting protection apparatus for RF equipment and the like |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2027655A1 CA2027655A1 (en) | 1991-05-01 |
| CA2027655C true CA2027655C (en) | 1999-02-16 |
Family
ID=23700420
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002027655A Expired - Fee Related CA2027655C (en) | 1989-10-30 | 1990-10-15 | Lightning protection apparatus for rf equipment and the like |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4985800A (en) |
| CA (1) | CA2027655C (en) |
Families Citing this family (42)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH05129856A (en) * | 1991-11-08 | 1993-05-25 | Sumitomo Electric Ind Ltd | Protecting circuit |
| IL106274A (en) * | 1993-07-08 | 1999-09-22 | Israel State | Lightning protection for antenna system |
| US5399962A (en) * | 1993-09-29 | 1995-03-21 | Merchant; Roger R. | Apparatus for detecting damped wave disturbances |
| EP0840404B1 (en) * | 1993-10-07 | 2000-12-27 | Andrew A.G. | Surge Protector |
| DE59708946D1 (en) * | 1997-01-27 | 2003-01-23 | Huber & Suhner Ag Herisau | Circuit arrangement for the protection of RF input circuits of telecommunication devices |
| US5838527A (en) * | 1997-04-29 | 1998-11-17 | Lawrence; Zachary Andrew | Electrical surge protection apparatus |
| US5844766A (en) * | 1997-09-09 | 1998-12-01 | Forem S.R.L. | Lightning supression system for tower mounted antenna systems |
| US6061223A (en) * | 1997-10-14 | 2000-05-09 | Polyphaser Corporation | Surge suppressor device |
| EP0913878A1 (en) * | 1997-10-29 | 1999-05-06 | Huber & Suhner Ag | EMP-arrester circuit |
| US6636407B1 (en) | 2000-09-13 | 2003-10-21 | Andrew Corporation | Broadband surge protector for RF/DC carrying conductor |
| ES2173041B1 (en) * | 2001-02-22 | 2003-12-16 | Prototal S L | DEVICE FOR THE INHIBITION OF RAY FORMATION. |
| FR2821993B1 (en) * | 2001-03-09 | 2003-06-20 | Thomson Csf | LIGHTNING LIGHTNING PROTECTION CIRCUIT |
| WO2002103875A1 (en) * | 2001-06-15 | 2002-12-27 | Kauffman George M | Protective device |
| JP3619796B2 (en) * | 2001-09-06 | 2005-02-16 | 株式会社エヌ・ティ・ティ・ドコモ九州 | Communication line surge protection system |
| US6785110B2 (en) * | 2001-10-12 | 2004-08-31 | Polyphaser Corporation | Rf surge protection device |
| US8027136B2 (en) * | 2007-10-18 | 2011-09-27 | Transtector Systems, Inc. | Surge suppression device having one or more rings |
| US7944670B2 (en) * | 2007-10-30 | 2011-05-17 | Transtector Systems, Inc. | Surge protection circuit for passing DC and RF signals |
| TWI445241B (en) * | 2008-03-21 | 2014-07-11 | Univ Chang Gung | Electromagnetic pulse protection circuit with filtering function |
| US8599528B2 (en) * | 2008-05-19 | 2013-12-03 | Transtector Systems, Inc. | DC and RF pass broadband surge suppressor |
| US8456791B2 (en) * | 2009-10-02 | 2013-06-04 | Transtector Systems, Inc. | RF coaxial surge protectors with non-linear protection devices |
| FR2953069B1 (en) * | 2009-11-24 | 2012-03-09 | Eads Europ Aeronautic Defence | DEVICE FOR PROTECTING THE LIGHTNING OF AN ANTENNA RECEIVER AND PLANE COMPRISING THE SAME |
| US8400760B2 (en) * | 2009-12-28 | 2013-03-19 | Transtector Systems, Inc. | Power distribution device |
| WO2011119723A2 (en) * | 2010-03-26 | 2011-09-29 | Transtector Systems, Inc. | Ethernet surge protector |
| US20110271802A1 (en) | 2010-05-04 | 2011-11-10 | Edward Honig | Double handle tool |
| US8441795B2 (en) | 2010-05-04 | 2013-05-14 | Transtector Systems, Inc. | High power band pass RF filter having a gas tube for surge suppression |
| CA2798891C (en) | 2010-05-11 | 2016-04-12 | Transtector Systems, Inc. | Dc pass rf protector having a surge suppression module |
| US8611062B2 (en) | 2010-05-13 | 2013-12-17 | Transtector Systems, Inc. | Surge current sensor and surge protection system including the same |
| US8976500B2 (en) | 2010-05-26 | 2015-03-10 | Transtector Systems, Inc. | DC block RF coaxial devices |
| US8730637B2 (en) | 2010-12-17 | 2014-05-20 | Transtector Systems, Inc. | Surge protection devices that fail as an open circuit |
| ES2586737T3 (en) * | 2011-08-01 | 2016-10-18 | Huawei Technologies Co., Ltd. | Lightning protection radio remote unit, distributed base station and lightning protection system and procedure |
| US9054514B2 (en) | 2012-02-10 | 2015-06-09 | Transtector Systems, Inc. | Reduced let through voltage transient protection or suppression circuit |
| US9048662B2 (en) | 2012-03-19 | 2015-06-02 | Transtector Systems, Inc. | DC power surge protector |
| US9190837B2 (en) | 2012-05-03 | 2015-11-17 | Transtector Systems, Inc. | Rigid flex electromagnetic pulse protection device |
| US9124093B2 (en) | 2012-09-21 | 2015-09-01 | Transtector Systems, Inc. | Rail surge voltage protector with fail disconnect |
| WO2016200700A1 (en) | 2015-06-09 | 2016-12-15 | Transtector Systems, Inc. | Sealed enclosure for protecting electronics |
| US9924609B2 (en) | 2015-07-24 | 2018-03-20 | Transtector Systems, Inc. | Modular protection cabinet with flexible backplane |
| US10356928B2 (en) | 2015-07-24 | 2019-07-16 | Transtector Systems, Inc. | Modular protection cabinet with flexible backplane |
| US10588236B2 (en) | 2015-07-24 | 2020-03-10 | Transtector Systems, Inc. | Modular protection cabinet with flexible backplane |
| US10193335B2 (en) | 2015-10-27 | 2019-01-29 | Transtector Systems, Inc. | Radio frequency surge protector with matched piston-cylinder cavity shape |
| US9991697B1 (en) | 2016-12-06 | 2018-06-05 | Transtector Systems, Inc. | Fail open or fail short surge protector |
| US10892540B2 (en) | 2016-12-30 | 2021-01-12 | Qortek, Inc. | High voltage antenna protection device |
| JP7002340B2 (en) * | 2018-01-12 | 2022-01-20 | 株式会社ヨコオ | In-vehicle antenna device |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2196272A (en) * | 1934-07-25 | 1940-04-09 | Rca Corp | Transmission network |
| US3289117A (en) * | 1964-03-23 | 1966-11-29 | Sylvania Electric Prod | Surge arrestor utilizing quarter wave stubs |
| US3747030A (en) * | 1971-06-07 | 1973-07-17 | Oak Electro Netics Corp | Band pass filter with transmission line section |
| US4399419A (en) * | 1980-03-20 | 1983-08-16 | Zenith Radio Corporation | Line isolation and interference shielding for a shielded conductor system |
| FR2519474B1 (en) * | 1982-01-05 | 1985-09-20 | Cables De Lyon Geoffroy Delore | DEVICE FOR PROTECTING A COAXIAL CABLE AGAINST LOW FREQUENCY AND HIGH POWER INTERFERENCE PULSES |
| US4554608A (en) * | 1982-11-15 | 1985-11-19 | Block Roger R | Connector for electromagnetic impulse suppression |
-
1989
- 1989-10-30 US US07/428,792 patent/US4985800A/en not_active Expired - Fee Related
-
1990
- 1990-10-15 CA CA002027655A patent/CA2027655C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| US4985800A (en) | 1991-01-15 |
| CA2027655A1 (en) | 1991-05-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |